1. VEPIC Update Goals and methods Targeted extended time observations
Chris Bretherton,
University of Washington
Goals and methods
Targeted extended time observations
EPIC/DYCOMS-II developments

2. VEPIC THEME
The theme of VEPIC is to better understand and simulate how Eastern Pacific cloud systems interact with the coupled ocean-atmosphere-land system on diurnal to interannual timescales.

3. VEPIC Scientific Issues (VPM5)
On what time and space scales does continental heating/mechanical forcing impact boundary layer cloud/radiative forcing?
How sensitive is the overall tropical circulation and ENSO to variations of Eastern Pacific cloud topped boundary layer properties and why?
What are dominant S/I feedbacks among Sc clouds, surface winds, upwelling, coastal currents and SST in E Pacific?
Does natural and anthropogenic aerosol variability significantly modulate the Sc?

4. VEPIC STRATEGIES (VPM5)
E Pacific as a testbed for model evaluation and improvement (e.g parameterization development) using multiscale data sets.
Model sensitivity studies to refine hypotheses and target observations.
Synthesis and enhancement of existing data sets, through targeted instrument procurement, algorithm evaluation and development, and enhanced observation periods.
Co-ordination with oceanographic, aerosol, cloud process communities, including CLIVAR CPTs.

5. V E P I C
Galapagos I.
Lima
Arica
WHOI buoy
San Felix I.

6. Two BAMS articles submitted.
EPIC2001 work continues
Two BAMS articles submitted.
AGU special session
Possible joint meeting in Sept.
with US PanAm CLIVAR
(Taneil Uttal)

7. TAO-EPIC has gathered a nice multiyear dataset
Yearly Feb-Apr precip
in SE Pacific ‘ITCZ’
…and freshening
Cronin

8. 2.5 years of data from the WHOI stratus buoy (20S 85W)
Weller

9. Buoy shows large net heat flux into ocean balancing eddy cooling
Weller

10. Ocean altimetry also shows an energetic eddy field
Weller

11. U. Chile has installed ceilometer and surface met at San Felix Is.
Decoupled
Cloud base (ceilometer)
LCL (surface met)
Well-mixed
Mostly clear
Garreaud
Shows daytime rise of LCL, cld. base, with synoptic variations

12. EPIC2001-Sc Diurnal Cycle (20S, 85 W) Daytime subsidence max [cm s-1]
ECMWF VERTICAL VELOCITY
Daytime subsidence max
EPIC2001-Sc
Diurnal Cycle
(20S, 85 W) 10
[dBZ]
-10
Wood

13. Diurnal variation of horizontal surface wind divergence from Quikscat
Wood
seabreeze ?
AM subsidence max
PM subsidence max
Hypothesis: Subsidence wave driven by diurnal heating cycle over Andes reaches buoy at noon.

14. MM5 simulation also shows late afternoon convergence at coast,
midnight ascent at buoy!
06LT
18LT
Garreaud

15. Remotely-sensed cloud microphysics from EPIC2001Sc
(Rob Wood, UW)

16. MODIS visible reflectance, 15Z 20 Oct. 2001
Polynya

17. Modis effective cloud droplet radius – large (clean) in polynya
small in coastal pollution

18. Polynya – drizzle feedback?
DYCOMS-II RF02
Polynya – drizzle feedback?
Stevens

19. DYCOMS-II Sc entrainment estimates from RF01
Stevens

20. Comparison of 6-day mean 20S 85W profiles with models
(Peter Caldwell, UW)
All models have adequate Sc, but too shallow a PBL.
CAM2 LWC all in lowest 3 levels ( m).
Observed LWC mainly at m.

21. Other updates RICO – trade Cu microphysics/turbulence
(Antigua, Dec Jan. 2005)
Proposed CPT on tropical cloud feedbacks on climate sensitivity…includes several US members of VEPIC.

22. Conclusions VEPIC-related progress in:
Atm.-ocean feedbacks in E Pacific
S America and SE Pac diurnal cycle of subsidence, cloud
Importance of cloud/drizzle/aerosol coupling to E Pac Sc.
Model/reanalysis validation
using
Existing data synthesis, targeted enhancements (WHOI buoy, SFI), field expts. (EPIC2001/DYCOMS-II.)
Coordinated modeling.
Come to WG meeting to hear more about VEPIC and participate in planning its future.